I just completed possibly the hardest hill ride I've ever done. It was awesome. My legs are toast, but in the best possible way. Theoretically I've done more elevation gain, but this ride had STEEP hills -- we rode up and down the Sammamish plateau from different directions. Only 64 miles total, 5100 (ish?) feet of climbing, but like I said, steep. Also I rode with a group that was listed as "strenuous" by Cascade Bike Club's ratings, which means 18 - 20 mph on flats. That's pushing it for me, for sure. I kept up, and I'm proud of it!

Edited to add: The fast bike, which I've named Lucy in honor of her previous owner, is earning her keep. So glad I'm riding her up those hills.